Radio frequency identification (RFID) transponders (or tags) can be used to track materials, for example, during shipping and storage. In an RFID tag interrogation process, an RFID reader can generate an electromagnetic energy, through a reader antenna, towards the item to be tracked. An antenna on the RFID tag can pick up the energy, and an integrated circuit (IC) in the RFID tag can transmit information through the tag antenna back to the reader.
Ultra-High Frequency (UHF) RFID can use radio frequencies of 433 MHz, 865-868 MHz, and the 2.4 GHz range (e.g., 2.45-5.8 GHz and 3.1-10 GHz). In this frequency range, the RF can propagate efficiently with a reasonable amount of power consumption, and can be produced inexpensively.
However, the RF characteristics and performance of UHF RFID tags can vary depending on the dielectric properties of the substrate, e.g., the package that the UHF RFID tags are placed on. The dielectric of the substrate can change the resonate frequency of the antenna of the RFID tags, resulting in an impedance mismatch between the RFID antenna and the RFID chip, e.g., the antenna is detuned from the RFID circuit and degrading the performance of the RFID tags. In the case of severe impedance mismatch or detuned antenna in an RFID tag, the tag can stop working or the performance may fall below acceptable parameters due to the interference or any other type of effect by the object, product or other element such as field attenuation or frequency shifts caused by the object or other sources.
Thus there is a need for improved RFID transponders that remedy the substrate's ability to detune or interfere with the RFID system ability in a simple, cost effective and timely manner during or after manufacturing.